Searching for the Fractional Quantum Hall Effect in Graphite

Measurements of basal plane longitudinal rho(b)(B) and Hall rho(H)(dB) resistivities were performed on highly oriented pyrolytic graphite samples in a pulsed magnetic field up to B = 50 T applied perpendicular to graphene planes, and temperatures 1.5 K <= T <= 4.2 K. At B > 30 T and for all studied samples, we observed a sign change in rho(H)(B) from electron-to holelike. For our best quality sample, the measurements revealed the enhancement in rho(b)(B) for B > 34 T (T = 1.8 K), presumably associated with the field-driven charge density wave or Wigner crystallization transition. In addition, well-defined plateaus in rho(H)(B) were detected in the ultraquantum limit revealing possible signatures of the fractional quantum Hall effect in graphite.